Oil easily produces a peroxide by action of oxygen in air, moisture, heat, light, metal ions, microorganisms, enzymes, or the like, and according to proceeding of oxidation reaction, unpleasant odor, deterioration of taste, browning, and the like occur. Further, in the case of intake of oxidized oil, the oxidized oil exerts an adverse influence on health, for example, digestive disturbance occurs.
Of fatty acids constituting oil, an unsaturated fatty acid having a carbon double bond is likely to be oxidized, and further, a polyunsaturated fatty acid having a plurality of double bonds has an exceptionally rapid oxidation rate.
Of the polyunsaturated fatty acids, in recent years, physiological activity of ω3 fatty acid such as eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) has attracted attention, intake of the ω3 fatty acid has been actively recommended for the purpose of the maintaining and enhancing of health, beauty care, or the like. However, the ω3 fatty acid is a polyunsaturated fatty acid and has an exceptionally rapid oxidation rate. Thus, it is difficult to maintain quality of the ω3 fatty acid and oxidation inhibition becomes a big problem.
Regarding oil or food containing oil, oxidation of the oil has been inhibited by adding an antioxidative substance containing a natural material including vitamins such as tocopherol, β carotene, and vitamin C, polyphenols such as catechin, sesamin, and rosemary extract, or the like.
However, particularly regarding the polyunsaturated fatty acid having a rapid oxidation rate, in present circumstances, a sufficient effect is not obtainable.
In addition, as a synthetic antioxidant agent, butylhydroxyanisol (BHA), dibutylhydroxytoluene, or the like is also used as a food additive, but there are also many consumers who concern about safety.
As another method, Patent Literature 1 discloses a method of adding a polyglycerin ester of saturated fatty acid having 8 to 22 carbon atoms to polyunsaturated lipid, and particularly describes that oxidation of oil is easily inhibited by adding a polyglycerol fatty acid ester to an oil-in-water (O/W) emulsified product of polyunsaturated lipid.
However, even using the method described in Patent Literature 1, a sufficient effect is not exhibited in oxidation inhibition of oil containing a polyunsaturated fatty acid.